Testing the Discovery of Archean Terrestrial Mass-independent Sulfur Isotope Anomalies

摘要/ abstract摘要：本文的主要目的是通过重复分析来证实与质量无关的硫同位素分选的发现，以验证其准确性，并确定异常硫的矿物宿主并测量其非均质性。对硫同位素分析进行进一步研究的动机是由于它们在古代岩石中作为生物标志物的效用。在前寒武纪岩石中，化石不存在，有机残留物已经转化为碳，硫同位素质量依赖的分馏仍然是硫酸盐还原微生物重要过程的不可磨灭的记录。随着太古宙岩石中与质量无关的硫同位素分异的发现，硫同位素地球化学具有更重要的意义。这种分馏在上层大气中是已知的，那里在紫外线的强烈影响下发生气相反应。因此，硫同位素分析可能会为生命的存在提供证据，但它们也可能记录了地球大气进化中一个以前不为人知的章节。本文将研究太古宙和元古代变质岩中异常硫的地理分布。将测量地层剖面，建立硫同位素分馏时间分布。卡内基研究所地球物理实验室的新型硫同位素激光氟化微探针将用于对太古宙和元古代变质岩进行详细检查。

AbstractEAR-0125096RumbleCarnegie Institution of Washington, Geophysical LaboratoryThe primary goal of this proposal is to confirm the discovery of mass-independent sulfur isotope fractionation by replicate analyses to validate accuracy and to identify mineral hosts of anomalous sulfur and measure its heterogeneity. The motivation for additional study of sulfur isotope analyses is because of their utility as biomarkers in ancient rocks. In Precambrian rocks where fossils are non-existent and organic residues have been converted to carbon, sulfur isotope mass-dependent fractionations remain as an indelible record of the vital processes of sulfate-reducing microbes. With the discovery of mass-independent sulfur isotope fractionations in Archean rocks, sulfur isotope geochemistry has acquired even greater significance. Such fractionations are known in the upper atmosphere where gas phase reactions take place under the strong influence of ultraviolet light. Sulfur isotope analyses, therefore, may give evidence for the former existence of life but they may also record a previously unknown chapter in the evolution of Earth's atmosphere. This proposal will examine the distribution of anomalous sulfur geographically in Archean and Proterozoic metamorphic rocks. Stratigraphic sections will be measured to establish a sulfur isotope fractionation time distribution. The new sulfur isotope laser fluorination microprobe at the Geophysical Laboratory of the Carnegie Institution will be used to do detailed examination of Archean and Proterozoic metamorphic rocks.